Development of Leishmania (Viannia) braziliensis and Leishmania (Leishmania) amazonensis in the sand fly Lutzomyia migonei (Diptera : Psychodidae)

Development of Leishmania braziliensis (Vianna) and Leishmania amazonensis (Lainson and Shaw) in the sand fly Lutzomyia migonei (Franca) was compared by studying the parasite microhabitats in the alimentary tract, the sequenc e of parasite morphological changes leading to the metacyclogenesis process , and the parasite transmission to the vertebrate susceptible host. Althoug h the infections by the 2 Leishmania species were initiated with the same n umber of amastigotes, Le. amazonensis developed a higher population. Infect ions with Le. braziliensis were typically peripylarian and those with Le. a mazonensis suprapylarian hut with an unusual invasion of an organ other tha n the gut, the Malpighian tubules. The life cycle of the 2 parasites within the sand fly vector included the development of all promastigote forms: pr ocyclics, haptomonads, nectomonads, paramastigotes and infective metacyclic s, the last of which are uniquely adapted for transmission to the vertebrat e hosts. Appearance of metacyclics coincided with the presence of large num ber of procyclics and haptomonads, low numbers of nectomonads and the appea rance of paramastigotes. In both type of infections, there was a high morta lity of the promastigotes inside the bloodmeal during digestion but once in fection became established metacyclic forms appeared. Although the numbers of metacyclics that developed in sand flies were low for both parasites the y were able to transmit the infection to vertebrates, a key event in the ve ctor competence. We suggest that L. migonei is a true biological host and a possible vector of the 2 Leishmania species, which coexist in extensive ge ographic areas.